Failure to parse some TTF files

[Dvd848]

The Python TTF parser fails to parse some TTF files (e.g. Roboto).

Steps to reproduce:

(ttf_venv) user@user-VirtualBox:~/temp$ python3 -m pip install kaitaistruct
Collecting kaitaistruct
  Downloading kaitaistruct-0.10-py2.py3-none-any.whl (7.0 kB)
Installing collected packages: kaitaistruct
Successfully installed kaitaistruct-0.10
(ttf_venv) user@user-VirtualBox:~/temp$ wget https://github.com/google/fonts/raw/d27d4149a40a9db16637f493f039255f5cb52d1f/ofl/roboto/Roboto%5Bwdth,wght%5D.ttf -q -O roboto.ttf
(ttf_venv) user@user-VirtualBox:~/temp$ wget http://formats.kaitai.io/ttf/src/python/ttf.py -q
(ttf_venv) user@user-VirtualBox:~/temp$ python
Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from ttf import Ttf
>>> data = Ttf.from_file("roboto.ttf")
>>> data._read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/user/temp/ttf.py", line 28, in _read
    self.directory_table.append(Ttf.DirTableEntry(self._io, self, self._root))
  File "/home/user/temp/ttf.py", line 347, in __init__
    self._read()
  File "/home/user/temp/ttf.py", line 350, in _read
    self.tag = (self._io.read_bytes(4)).decode(u"ascii")
UnicodeDecodeError: 'ascii' codec can't decode byte 0xf5 in position 3: ordinal not in range(128)

For what it's worth, the problem can be worked around by modifying the decode()s to ignore errors:

(ttf_venv) user@user-VirtualBox:~/temp$ sed -i -e 's/decode(u"\([^"]*\)")/decode(u"\1", errors="ignore")/g' ttf.py
(ttf_venv) user@user-VirtualBox:~/temp$ python
Python 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from ttf import Ttf
>>> data = Ttf.from_file("roboto.ttf")
>>> data._read()
>>> data
<ttf.Ttf object at 0x7f68577cc460>

I'm not sure if this can be considered a real fix though.

Originally found as part of a pytai issue.